Spraying and vapor deposition have been used for many years to produce coatings on substrates by producing a mist or vapor of the deposited material and then exposing a surface of the substrate to the vapor to thereby form the desired coating. In order to conserve the deposited material, and to avoid contaminating the surrounding area, a chamber is used to surround the substrate. In many methods the chamber must be evacuated to provide an oxygen-free or reduced atmosphere to avoid a combustible mixture or the early reaction of the precursor. During the deposition process, the coating material may deposit on the walls of the chamber, producing waste material that must be collected for reuse or disposed of. Other waste is produce by the material that is removed from the chamber by the ventilation system.
In chemical vapor deposition (CVD), vapor may be produced in a bubbler or other device that subjects the precursor materials to an energy source to activate the precursor and form the coating material, and then this material (in vapor form) is routed to the substrate. More recently developed CVD methods include combustion chemical vapor deposition (CCVD), as described in U.S. Pat. Nos. 5,652,021, 5,858,465, 5,863,604, 5,997,956 and 6,013,318, the disclosures of which are hereby incorporated by reference. In these patents a combustion source is used to provide the energy source to activate the precursor material (and possibly heat the substrate as well) in the vicinity of the substrate surface. This eliminates the need for a chamber and increases efficiency of the deposition process by producing the coating material close to the substrate so that a majority of the material is deposited on the desired surface of the substrate. Of course, a chamber or hood may still be desired depending on the specific application.
Regardless of the coating method used, what is missing in the prior art is a higher efficiency method of coating a large surface area of a substrate in a continuous manner. This is necessary to provide a practical solution for large-scale production of coated materials at reduced costs and reduced production of solid wastes. One example is CVD, wherein normal deposition efficiencies are 5 to 30%. Higher deposition efficiencies are desired to lower costs, increase deposition rates and be environmentally sensitive by reducing waste material.